Gaining

Something that has bothered me since I started tracking my weight is that my rate of gain isn't as fast as I'd like. Once I hashed things put with scales with bad accuracy and/or precision, I determined my rate is barely 3 pounds a month. I really want to be gaining 10 pounds or so. Does anyone have any advice for me on this?

The thing is that when I first started getting fat, I gained around 10 pounds a month. I deeply want to swell up at that rate again. My goal is around 600 pounds and my progress is way too slow.